In recent years, wireless local area networks (LANs) representative of Institute of Electrical and Electronics Engineers (IEEE) 802.11 have been widely used. In addition, the number of wireless LAN-compatible products (hereinafter, also referred to as wireless communication devices) have also increased in accordance with this. In contrast, wireless communication resources available for communication are limited. Therefore, it is desirable to increase the efficiency of communication between wireless communication devices.
As an example of a technique for improving communication efficiency, a technique called virtual carrier sensing is known. Specifically, a technique for controlling a network allocation vector (NAV) using a mechanism such as request to send (RTS)/clear to send (CTS) is known. For example, a transmission device that desires data transmission transmits an RTS frame to a reception device which is a destination of data transmission, and the reception device transmits a CTS frame to the transmission device in a case in which data transmission is permitted. At this time, communication devices other than destinations of the RTS frame and the CTS frame set a NAV and stop data transmission during a NAV period. Accordingly, it is considered that communication collision is avoided, and communication can be performed efficiently as a result.
Here, there is a mechanism of releasing the NAV before the NAV period ends. For example, in a case in which communication using the RTS and the CTS is performed between an access point (AP) and a station (STA), the AP can release the set NAV by transmitting a contention free (CF)-end frame. Further, in the CF-End frame, a broadcast address is stored as destination information, and a basic service set identifier (BSSID) is stored as transmission source information.
However, in the mechanism where the NAV is released before the NAV period ends, unfairness may arise in terms of opportunities to access a transmission path. For example, the communication device that has received the CF-End frame can release the NAV and start communication, but the communication device which has not received the CF-End frame is unable to perform communication until the NAV period ends since the NAV remains set.
On the other hand, a method in which the STA transmits a first disconnection process frame including a CF-End frame for disconnecting a transmission opportunity (TXOP) set around the STA, and the AP which has received the first disconnection process frame transmits a second disconnection frame including a CF-End frame for disconnecting the TXOP set around the AP is disclosed in Patent Literature 1.